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Claire is correct about solutions for all subbands being logged. That
historical data is available for analysis when someone has time to
investigate the best way to combine the subband pointing data.<br>
<br>
Rick,<br>
I don't see how you got these totals:<br>
<pre wrap="">124 seconds for 'slow' mode,
94 seconds for 'fast'.</pre>
for slow: 20 seconds/pointingPosition * (5 positions + 2 skipped
positions) = 140 seconds<br>
for fast: 15 seconds/pointingPosition * (5 positions + 2 skipped
positions) = 105 seconds<br>
<br>
It seems like you used 1 dummy position and added a four second
buffer. The code is currently skipping the first two subscans in every
pointing scan (i.e. skipped positions).<br>
<br>
Thanks,<br>
Keith<br>
<br>
<br>
Claire Chandler wrote:
<blockquote cite="mid:Pine.LNX.4.64.1011181214130.12452@ancho"
type="cite">
<pre wrap="">Hi Rick,
You need to define what you mean by "works for wideband". Recall that at
present the default algorithm in TelCal is to take the second subband from
the bottom of each baseband for the solution that is fed back to the
online system. Therefore it relies on that subband being RFI-free. I
believe that solutions are being written for all subbands for testing
purposes at the moment, and what we really need to do is to establish how
to combine the results from all those subbands to obtain a solution that
is not affected by RFI, and can potentially be used to enable pointing on
weaker sources.
Claire
On Thu, 18 Nov 2010, Rick Perley wrote:
</pre>
<blockquote type="cite">
<pre wrap=""> I ran a test of referenced pointing this morning. There were two
goals:
1) Does 'wide-band' referenced pointing work as well and reliably as
'narrow-band'?
2) Does a 15-second cadence work as well as 20-second?
(Explanation: In the past, the system used 10 seconds to move from one
position to the other, and 10 seconds to integrate. But from holography
we know that the move-and-settle time is less than 5 seconds, so a
15-second (5+10) regimen should work).
To test these, I used 3C147 (~5 Jy) to measure pointing offsets at
X-band, with four combinations:
1) Narrow-band with 20 seconds.
2) Narrow-band with 15 seconds.
3) Wide-band with 20 seconds
4) Wide-band with 15 seconds.
The intention was to observe each mode sufficiently long for 3
consecutive pointing solutions. Due to a blunder on my part, the 'fast'
tests were observed long enough for only 2 solutions. But that is still
sufficient for the following conclusions:
A) Wide-band mode works as well as narrow-band.
B) Fast mode appears to be as good as 'slow'.
There were a few failed solutions for all four trials -- the
statistics are not good enough to claim that any one of these four is
better or worse than the others. Comparison of the actual solutions has
been done for only one antenna (so far) -- there is no significant
differences, other than an expected change in elevation offset as the
sun rose.
By looking at the detailed log, the sequence of operations is easily
discerned. (Ken claims this may be unreliable, and he intends to peer
deeper after lunch). But, be this as it may, I deduce that the
*absolute minimum* time needed for a single referenced pointing
measurement is (presuming the antennas are on source) is:
124 seconds for 'slow' mode,
94 seconds for 'fast'.
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